LGI1 and CASPR2 autoimmunity in children: Systematic literature review and report of a young girl with Morvan syndrome

Leucine-rich glioma-inactivated protein 1 (LGI1) and contactin-associated protein-like 2 (CASPR2) neurological autoimmunity in adults has been associated with various clinical syndromes involving central, peripheral and autonomic nervous system, while data in children is limited. We perform the first systematic literature review on paediatric LGI1 and CASPR2 autoimmunity, with focus on clinical data, in order to contribute to the definition of clinical features of LGI1 and CASPR2 autoimmunity in paediatric age and favour early diagnosis. Additionally, we report the youngest-to-date case of Morvan syndrome. We identified 37 published paediatric cases of LGI1 and/or CASPR2 autoimmunity. Most frequent syndromes were encephalitis in LGI1-positive and isolated epilepsy in CASPR2-positive children, while syndromes with predominant peripheral symptoms were most frequent in double-positive children. With the limitations imposed by the low number of cases, differences to published adult cohorts included: absence of faciobrachial dystonic seizures and hyponatremia in patients with LGI1 -positive encephalitis; slightly higher proportion of isolated epilepsy syndromes in CASPR2-positive patients; absence of tumour in the whole cohort.